Method for stiffening

ABSTRACT

A METHOD FOR STIFFENING A SELECTED AREA OF SHEET MATERIAL, PARTICULARLY AREAS OF SHOE COMPONENTS IN WHICH A FIRST COATING OF MOLTEN RESIN IS LAID DOWN ON THE AREA TO BE STIFFENED, A FLEXIBLE FIBROUS REINFORCEMENT IS LAID DOWN ON THE COATING WHILE EXPOSED PORTIONS OF THE COATING ARE IN SOFT ADHESIVE CONDITION AND THEREAFTER A SECOND COATING   OF VISCOUS MOLTEN RESIN IS APPLIED TO COVER THE REINFORCEMENT AND EXTEND OVER THE EDGES OF THE REINFORCEMENT TO MERGE INTO THE FIRST COATING.

q 1971 v. BECKER UETHOD FOR STIFPENING 2 Shoots-Shut 1 Find Oct. 20, 1969 inventor- Karl VBeclcer By his Aziorney away mxdsxms 5425! Sept. 20, 1971 v, BECKER 3,605,152

ETBQD FOB STIFFENING Fil Oot. 20, 1969 2 Shoots-Shut B III/I Jim llll Illlll'l'il United States Patent Office 3,605,152 Patented Sept. 20, 1971 3,605,152 METHOD FOR STIFFENING Karl V. Becker, Boxford, Mass, assignor to USM Corporation, Boston, Mass. Filed Oct. 20, 1969, Ser. No. 867,642

Int. Cl. A43d U.S. Cl. 12-146D 11 Claims ABSTRACT OF THE DISCLOSURE FIELD OF THE INVENTION The present invention relates to a method for stiffening sheet material and particularly to a method for stiffening selected areas of shoe elements.

BACKGROUND OF THE INVENTION In the stiffening of shoe uppers, particularly the toe and heel ends for the purpose of preserving a desired shape, there have been employed preformed stiffener elements such as fiber counters which are inserted in a shoe upper prior to lasting. Another procedure involved the use of so-called blanks of moldable sheet material which is softenable by heat or by solvent and inserted in the shoe uppers prior to lasting to be shaped in the course of lasting to a desired configuration which they retain on hardening. A further procedure which has been well accepted is that forming the subject matter of the US. patent to Chaplick and Rossitto No. 3,316,573 dated May 2, 1967 in which molten resin is applied as a thin layer to the portion to be stiffened and is cooled to stiff, resilient condition. This last method offers important advantages both in eliminating the need for carrying a variety of styles and sizes of separate stiffening elements and in providing a good stiffening action without the bulk and edge effects characteristic of separately introduced shoe stiffener elements.

Shoes of which toe portions have been stiffened by the process of the patent have been found very satisfactory. However, counter portions of shoes are subjected to a different character of stress particularly sharp bending stresses in the course of putting on shoes and localized stresses somewhat above the heel seat developed in a shoe in the course of being worn. Greater resilience, stiffness and resistance to breakdown are desired in this area and may be wanted in the box toe area for particular purposes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stiffening method particularly for shoe components in which the advantages of the hot melt stiffening are retained but in which there is formed a stiffened component having greater stiffness, resilience and resistance to breakdown under bending stress.

To this end and in accordance with a feature of the present invention a flexible fibrous reinforcement is laid down on a hot melt applied coating of resin stiffener on a sheet material to be stiffened, such as a shoe component, while exposed portions of the coating are in soft adhesive condition and thereafter a second coating of molten resin is laid down to cover the reinforcement and extend smoothly from portions above the reinforcement past the margins of the reinforcement to merge into the first coating. A further layer, e.g. a further shoe component, may be united to the second coating with that coating in soft adhesive condition prior to or at the time the layers, in heated condition, are pressed together and shaped. On cooling, the coatings, reinforcement, and shoe components are united into a strong, breakdown-resistant stiffened composite which can be shaped as part of a shoe and will retain the shape against deforming stresses.

The invention will be described in connection with the drawings, in which:

FIG. 1 is a diagrammatic view showing the successive application of a first molten resin coating, a reinforcement and a second molten resin coating to a shoe part;

FIG. 2 is an elevational view partially in section showing the application of molten resin to a shoe part and the relation of the resin to the shoe part after coating;

FIG. 3 is an elevational view with parts broken away showing the application of a reinforcement to the molten resin coating and the relation of the shoe part resin coating and reinforcement;

FIG. 4 is a sectional elevational view on an enlarged scale showing the relation of the reinforcement to the resin coating;

FIG. 5 is an elevational view partially in section showing the application of the second molten resin coating and the relation of the shoe part, first coating, reinforcement and second resin coating;

FIG. 6 is a sectional elevational view on an enlarged scale showing the relation of the second resin coating to the reinforcement and to the first resin coating; and

FIG. 7 is a side section with parts broken away of a formed and lasted shoe upper including the stiffened shoe portion and a liner after conformation and consolidation of shoe parts.

In the following disclosure the invention will be described in connection with the stiffening of shoe parts, particularly shoe counters and box toes. It will be understood that the invention is useful in other relations involving the application of stiffening material in molten form.

The sheet material 10 to be stiffened, e.g. a shoe part such as the quarter, counter lining, counter pocket, or toe of a shoe upper, is held, ordinarily in generally flat condition, for subjection to the successive steps of the process. The same general area is treated in each of the steps and, although the processing may be carried out by hand, it has been found convenient to mount the material in a work holder 12 which supports it with the surface to be treated exposed and which is movable to successive stations for successive steps of the process.

As shown in FIGS. 1 and 2 the first step is the application to the area to be stiffened of a first coating 14 of normally stiff, resilient, synthetic polymeric material in viscous molten condition. Spreading may be carried out by hand but is preferably carried out using a mechanical applicator 16 including a rotating applicator wheel 18 disposed in the otherwise open lower end 20 of a heated chamber 22 containing the molten stiffening material. The molten material is spread in wetting adhesive engagement with the exposed surface of the sheet material 10 and a metering blade 24 which may be the lower edge of the chamber 22 determines the thickness of the applied coating. Reference is made to US. Pat. 3,316,573 referred to above for a more complete description of the work holding means, applicator head and application procedure.

The work holder 12 and sheet material 10 are then moved to the next station (see FIG. 3) where a flexible fibrous reinforcing web 26 is laid down on the coating 14 while the coating is in soft adhesive condition. In the preferred operation, the sheet material 10 is moved to the second stage directly after the molten synthetic polymeric material coating 14 is applied so that the surface of the coating is still in soft and adhesive condition from retained sensible heat in the body of polymeric material laid down. It is, however, within the spirit of the invention to bring the polymeric material to soft adhesive con dition by application of further heat to its surface before the reinforcing web 26 is laid down. After the web 26 is laid down on the coating 14, it is preferably lightly pressed as by presser member 28 to insure a level surface and good overall engagement of the web and coating. As shown in FIG. 4, the hot material will flow up through any opening such as spaces between threads in the reinforcing web.

The reinforcing web 26 preferably has an outline shape and size such that a major portion of its margins do not extend beyond the area covered by the first polymeric with the coating as by extending beyond the area of the first coating (not shown). For example, it may be desirable that the portion of the reinforcing web adjacent the lasting margin of a shoe part by kept free either for removal to a fixed line or other purpose.

After the reinforcing web 26 has been secured onto the first coating 14, the composite of sheet material, coating and web may be carried, while still held in the work holder 12, to a third stage, (see FIG. 5) for application of a second coat 34 of viscous molten synthetic polymeric material. This second coating fills depressions on the surface of the reinforcing web and joins with the first coat in the openings 30 through the web 26 as shown in FIG. 6. The applicator 36 and appliying procedure may be the same in this station as at the first station. It is desirable that the second coating 34 extend not only over the exposed portion of the reinforcing web 26 but that it extend past the edges of the web and merge smoothlly with the first coating 14 so that the exposed surface of the stiffening applied to the shoe part is free from sharp breaks or steps.

A further shoe component may be pressed against the exposed surface of the second coating while it is in soft adhesive condition. For example, where the first coating has been applied to the heel portion of the upper, a counter liner or counter pocket 38 may be pressed against that surface.

For completion of a shoe, the stiffened portion will ordinarily be heated to a moldable but not freely flowable condition at an elevated temperature below the melting point of the polymeric material. This may be done by steaming, radiant heat or other heating procedures. After heating, a further shoe element such as a counter liner or counter pocket 38 is ordinarily brought over the exposed surface of the second coating if a shoe element has not previously been disposed on that surface and the shoe upper is subjected to pressure to conform it to the desired shape. For example (see FIG. 7), the shoe upper may be placed on a last or other shaper 40 with the polymeric stiffener material in moldable condition and tension applied to the shoe upper to press it into firm engagement with the last to shape the stiffener. With the polymeric material in heat softened condition, the pressure acts to join the shoe upper and further shoe element and reinforcing web in the desired relation. On cooling, the joined layers of the shoe upper cooperate to give strength and resilient stiffness to retain the shape into which the shoe upper has been put.

A wide variety of heat softenable synthetic polymeric resinous materials may be used in the present process. These materials may be either permanently thermoplastic or may be heat softenable and converted by heat or other means to a higher melting or infusible condition. Among useful materials are the polyesters and copolyesters, polyamides and copolyamides, polyesteramides, polyvinyl compounds such as polystyrenes, polyvinyl acetate and so on. Patent 3,316,573 above referred to provides a fuller description of polymeric materials including preferred ranges of softening points and application temperatures useful for forming the stiffener coatings in the present method and the disclosure of that patent is incorporated by reference.

In the formation of the coatings or layers of polymeric material on the shoe part, it is important that the molten material have a viscosity low enough to wet and adhere to the surface on which it is applied but sufficiently high that it will not penetrate through the shoe component to be stiffened. The coatings will ordinarily be from about 0.005 inch to about 0.020 inch in thickness.

The reinforcing web 26 may be a woven fabric, a nonwoven fabric, a felt or, for example, a weftless fabric or even separate threads. For best results it appears desirable to use webs of which a substantial portion of the area is made up of closely associated fibers or filaments capable of at least limited relative movement with respect to each other but in which the web 26 has a plurality of spaced macroscopic openings 30. For example, in woven fabrics, the threads 32 are made up of bundles of closely associated fibers or filaments while the spaces 30' between and around the threads provide macroscopic passages through the woven material. Nonwoven fabrics or felts provide a body in which the fibers or filaments are closely associated, and macroscopic openings may be formed in such nonwoven fabric or felt as by needling.

Where reinforcing webs including such macroscopic passages 30 are used, the web 26 will be laid down on the polymeric material of the first coating 14 while that coating is at a temperature at which the polymeric material has a viscosity low enough to wet and adhere to the web 26 and to enter the macroscopic openings 30 but while the polymeric material viscosity is sufficiently high that it will not penetrate substantially into central portions of the thickness of the areas of closely associated fibers around the openings as shown in FIG. 4. For example, the viscosity will be low enough for the polymeric material to enter the spaces 30 between threads of a woven fabric but will be too high for substantial penetration of the polymeric material into spaces between individual filaments in at least central portions of the thickness of the threads of the fabric.

In like manner the second coating 34 will be applied to the free surfaces of the reinforcing web 26 at a temperature at which the molten polymeric material has a viscosity low enough to wet and adhere to the surface and to enter into the macroscopic openings 30, desirably to an extent as shown in FIG. 6 where it will meet and unite with material of the first coating which has entered into the openings 30 from the opposite side of the web. In this case also the temperature of the molten polymeric material is selected to provide a viscosity of the polymeric material sufficiently high that it will not fill the spaces between closely associated filaments, eg those making up the threads of a web.

Following this procedure, the material in the openings or passages in the web constitute a multitude of small columns or links between the layers 14 and 34 of material on the opposite sides of the web; and these columns cooperate with the material of the web in holding the two stiffener layers or coatings in spaced relation to give a greater stiffening effect than the single layer having the same amount of resin as is present in the two coating layers.

It is to be observed that where the web does not include openings or passages through it, it will still provide a desirable improved stiffening action by spacing the two stiffening layers but not as great a stiffening action as is obtained where the small columns or links extend between the two coatings or layers.

Both in the web with openings and without openings, the central portions of the thickness of the clusters of closely associated fibers, e.g. the central portions of the threads of a woven fabric or of portions of a nonwoven fabric or felt between openings are substantially free of stiffener material so that the individual fibers or filaments making up such central portions can move relative to each other when the stiffened component is subjected to bending. Also the fibers or filaments in the central portions are somewhat compressible. These factors combine to give to the stiffened sheet material a greater resistance to cracking and tearing than is obtained with stiffeners in which full penetration of spaces between fibers is secured. This is presumed to be due to the compressibility allowed by the interfiber movement in the web and by the action of the web as a spacer for the two layers of stiffener material in increasing the radius of any bend formed in the material so that cracking or other rupturing stresses are not localized.

The following example is given as of assistance in understanding the invention; but it is to be understood that the invention is not limited to the particular materials, procedures or conditions set forth in the example.

EXAMPLE A polyamide resin from condensation of dimerized soybean oil fatty acid with ethylene diamine and having a Ball and Ring softening point of 100 C. to 116 C. was supplied to a first applicator of the type described above.

A leather shoe upper was secured with its counter portion in a work holder such as described above with the counter portion to be stiffened exposed for engagement with the applicator wheel of the applicator. With the temperature of the applicator adjusted to about 300 F., a coating .020 inch thick was spread on the area to be stiffened. Thereafter, while the resin was still molten, a reinforcement element of lightweight burlap with a thread count of 20 by 20 and with its edges cut to an outline similar to but smaller than the area covered with molten resin was pressed onto the molten resin to cause it to adhere and to cause the molten resin to flow part way into the passages between the threads. Thereafter, the work holder carrying the shoe part with the coating of resin and reinforcement was sent to a second applicator supplied with the same resin and operating at the same temperature where a coating .010 inch thick was applied over the reinforcing and extending out to merge smoothly into the first applied coating. The counter liner was then pressed down on the second coating.

An unlasted shoe upper containing the reinforced counter portion was subjected to radiant heat for about 60 seconds to bring its temperature to from about 175 F. to about 185 F. and the upper was placed on a footform heated to 270 F. for 17 seconds to soften the resin and backpart mold and heel seat last. Thereafter, the lasting of the shoe was completed and further operations such as soling, heeling and the like were carried out and the shoe removed from the last. The heat and pressure soften the resin and combine the parts in the desired relative position prior to removing from the machine.

The counter portion of the shoe was found to have good resilient stiffness together with superior resistance to crackmg.

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

1. A method for stiffening a selected area of sheet material comprising the steps of applying, in viscous molten state, a first coating of synthetic polymeric material which will harden to stiff, resilient condition on the area of sheet material to be stiffened, laying down a flexible fibrous reinforcing web on the coating while exposed portions of the coating are in soft adhesive condition, thereafter applying in viscous molten state a second coating of synthetic polymeric material on said web and hardening said synthetic polymeric material whereby said first coating, said web and said second coating are firmly adhered together and to said sheet material and form a stiff, resilient area of sheet material.

2. A method for stiffening a selected area of sheet material as defined in claim 1 in which said first coating is still soft from heat retained in the applied molten polymeric material at the time said reinforcing web is laid down.

3. A method for stiffening a selected area of sheet material as defined in claim 2 in which said web includes areas of closely associated fibers surrounding openings through said web and in which said openings are substantially filled by said polymeric material.

4. A method for stiffening a selected area of sheet material as defined in claim 3 in which a further sheet material is disposed on the free surface of said second coating and the composite of said sheet material, said first coating, said reinforcing web, said second coating and said second sheet material are pressed together and shaped with said synthetic polymeric material in heat softened condition to form on cooling a stiff resilient shaped sheet material.

5. A method for stiffening a selected area of sheet material as defined in claim 1 in which said sheet material is a shoe component.

6. A method for stiffening a selected area of a shoe component as defined in claim 5 in which said reinforcing web has an outline shape and size such that a major portion of its margins do not extend beyond the area covered by said first coating and said second coating extends smoothly from portions above said web past the margins of said web and merges into said first coating in areas of said first coating which extend beyond the margins of said web.

7. A method for stiffening a selected area of a shoe component as defined in claim 6 in which a second sheet shoe component is disposed on the free surface of said second coating and the composite of said sheet material, said first coating, said reinforcing web, said second coating and said second sheet material are pressed together and shaped with said synthetic polymeric material in heatsoftened condition to form on cooling a stiff resilient shaped shoe component.

8. A method for stiffening a selected area of a shoe component as defined in claim 6 in which said rein-forcing web includes areas of closely associated fibers surrounding openings through said web and in which the viscosity of said molten polymeric material is sufficiently low that said openings are substantially filled by said polymeric material but the viscosity of the molten polymeric material is sufficiently high that the polymeric material does not penetrate central portions of the thickness of said areas whereby fibers in said portions remain capable of movement relative to each other.

9. A method for stiffening a selected area of a shoe component as defined in claim 7 in which said reinforcing web includes areas of closely associated fibers surrounding openings through said web and in which the viscosity of said molten polymeric material is sufficiently low that said openings are substantially filled by said polymeric material but the viscosity of the molten polymeric material is sufficiently high that the polymeric material does not penetrate central portions of the thickness of said areas, whereby the fibers in said portions remain capable of movement relative to each other.

10. A method of stiffening a selected area of a shoe component as defined in claim 9 in which said rein-forcing web is a woven fabric in which the threads constitute areas of closely associated fibers surrounding openings between the threads.

8 11. A method for stiffening a selected area of a shoe References Cited component as defined in claim 9 in which said reinforcing UNITED STATES PATENTS Web is a nonwoven fiber sheet of closely associated fibers 3,316,573 5/1967 Chaphck et al. l2l46(D) and in which macroscopic openings have been formed hmugh Sald 5 PATRICK D. LAWSON, Primary Examiner 

